}
int dev_urandom(void *p, size_t n) {
- _cleanup_close_ int fd;
+ static int have_syscall = -1;
+ int r, fd;
ssize_t k;
+ /* Use the syscall unless we know we don't have it, or when
+ * the requested size is too large for it. */
+ if (have_syscall != 0 || (size_t) (int) n != n) {
+ r = getrandom(p, n, 0);
+ if (r == (int) n) {
+ have_syscall = true;
+ return 0;
+ }
+
+ if (r < 0) {
+ if (errno == ENOSYS)
+ /* we lack the syscall, continue with reading from /dev/urandom */
+ have_syscall = false;
+ else
+ return -errno;
+ } else
+ /* too short read? */
+ return -EIO;
+ }
+
fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0)
return errno == ENOENT ? -ENOSYS : -errno;
k = loop_read(fd, p, n, true);
+ safe_close(fd);
+
if (k < 0)
return (int) k;
if ((size_t) k != n)